Regrettably, even though operative vaginal delivery can save the day whenever a spontaneous vaginal delivery proves difficult or impossible, and a cesarean section is either contraindicated by maternal conditions or preparation for it cannot be made in a timely fashion, the tendency, in recent years, has been, in many institutions, toward diminished resident teaching of operative vaginal delivery, particularly forceps techniques. This tendency is generally attributed to the lack of skilled instructors, resulting from the retirement of classically trained obstetricians. Consequently, the rate of forceps delivery has decreased in recent years, a trend that this simulator may help reverse. Equally, there has been some reluctance to use the vacuum because the FDA issued in 1998 a Public Health Advisory on the use of the vacuum extractor, prompted by the serious fetal hemorrhagic complications associated with it, secondary to cup detachment (“pop-offs”). The net result has been a reduced rate of operative vaginal deliveries and a parallel increase in the rate of cesarean sections.
The training of obstetricians in operative vaginal delivery, is challenging for a number of reasons, including the decreased patient's availability for teaching, the limited work hours of the residents, which makes it difficult for them to be present at unpredictable emergencies, the insufficient time that exists for discussion and analysis in such situations, and the uniqueness of each person's learning curve.
Particularly difficult has been, traditionally, when training residents in operative vaginal delivery, to teach them the following important prerequisites.
In the case of the forceps:
a) What constitutes safe traction? The trainee is generally told that the traction must be “gentle” and that for a progressive advancement of the fetal head in the birth canal, traction must be applied in a steady manner, preferably with a gradual increase in intensity, sustained for a brief interval and slowly relaxed, to simulate labor contractions. The problem here is that what constitutes “gentle” traction varies considerably from one individual to another and thus, it not unusual that undue traction be inadvertently applied, as W. H. Pearse noted over 50 years ago (“it is amazing how simple it is to sit at the end of the table and exert . . . over 100 pounds of traction”). Yet, we know from the clinical studies of W. H. Pearse and J. V. Kelly et al. that a traction force of 50 pounds (22.8 kg) should be considered the upper limit of pull with regard to fetal safety, when using forceps.
b) What is the correct line of traction? The textbooks generally emphasize that, once the fetal head has been rotated into the proper position (i.e. to the occipital-anterior position), traction must follow the curvature of the birth canal, so that the fetus progress along the path of least resistance, while, at the same time, avoiding the symphysis. The problem here is that to demonstrate, during an actual delivery, how to pull correctly, the attending has to ask the trainee to step aside and take over the instrumental delivery (for this reason teaching how to use forceps has been compared to teaching how to fly an airplane with only one set of controls).
c) How much traction is too much? Specifically, when to stop applying traction and to abandon the vaginal operative delivery in favor of a cesarean section. The trainee is generally told that the answer to that question is generally a matter of clinical judgment, acquired with experience. The problem here is that experience cannot be thought, and, as the result, the less learned, have been known to put up, on occasion, their feet against the edge of the delivery table and to pull with all their strength, as noted by J. Baxter.
In the case of the vacuum extractor:
a) What is the correct application of the cup on the fetal head? Right on the sagittal suture, with the center over the flexion point, a.k.a. the pivot point (i.e. an imaginary spot which is 2-3 cm forward of the posterior fontanelle).
b) How to apply traction perpendicular to the cup, while keeping the axis of the fetal head in line with the axis of the pelvis?
c) What is the amount of permissible traction? Specifically, the amount of traction that avoids cup detachment (a.k.a. pop-offs). As in the case of forceps, a trainee is generally told that the traction must be “gentle”. Yet, we know from clinical data that the traction should be limited to the negative pressure under the cup, otherwise detachments are inevitable and with them the possibility of fetal injury. As D. Mishell et al, M. A. Duchon, and A. Vacca have shown, the amount of safe traction, with the cups currently used, at the recommended vacuum of 600 mmHg, ranges between 22 and 28 pounds, depending on the characteristics of the device used (i.e. its diameter and whether it is made of solid or elastic material).
Furthermore, the use of simulation in Obstetrics has been known and is widely accepted. A number of simulators have been invented for this purpose, such as U.S. Pat. Nos. 6,503,087 and 7,114,954, both to Eggert et al., U.S. Pat. No. 7,241,145 to Reiner et al., and U.S. Pat. No. 7,465,168 to Allen et al. None, however, has been specifically designed for operative vaginal delivery. Therefore, the simulators disclosed in the aforementioned patents can only be used to teach the correct insertion of the blades, in the case the forceps, and the proper application of the cup to the fetal head, in the case of the vacuum extractor. However, these simulators are not suited to teach the trainee the most important safety aspects of the operative vaginal delivery mentioned above, namely, what constitutes, when using forceps, “gentle” traction, what is the correct line of traction necessary to keep the head in line with the pelvic axis, and, more importantly, how much traction is too much and when using the vacuum extractor, what is the correct direction and the amount of permissible traction so that “pop-offs” can be avoided.
Thus, the need exists for a birth simulator that recognizes and addresses these limitations, allowing the trainee to reliably learn the essential aspects of operative vaginal delivery and accurately replicate the experience of a live forceps or vacuum delivery.
Embodiments usable within the scope of the present disclosure meet these needs.